Over the Labor day weekend, I finally put together my upgrade project - the full Jehnert flatline series + XD600/6 amp. I was expecting an easy installation, but it turned out to be a total disaster, well not entirely, I'm happy with the underseat bass as it is full and punchy.

But the good news end here... There are 2 problems,

- A constant white noise coming from the door speakers and tweeters even when the volume is turned off, I had to adjust the gain all the way to 0 to alleviate this.
- When playing any kind of percussion high pitch sound, it sound harsh, noisy, pronounced and dispersed, I don't how else to describe it, on a lot of the songs it is unbearable when playing at any level of loudness. This can't be normal! Are my tweeters defective?? Do you think this could be the same as the white noise problem?

Needly to say I am very disappointed at the moment, with time and $$$ premium I paid for the speakers... Can someone tell me what's wrong and how to fix this??

One thing worth mention is I stripped the crossover box to bare circuit so it would fit on the door, I hope that is not the cause, other than that I did a pretty standard installation following what the experts have already done on this forum.

- HiFi HU -> Technic's harness -> XD600
- ch1,2 for front, bridged ch3,4 and ch5,6 for the underseats respectively
- 4 gauge wire for power connection nice and secure. Tried both battery ground and left rear seat ground, but result the same.
- when unplug Technic's RCA inputs from the amp, hissing noise gone, but of course that's the only source input I can't do without it...

Over the Labor day weekend, I finally put together my upgrade project - the full Jehnert flatline series + XD600/6 amp. I was expecting an easy installation, but it turned out to be a total disaster, well not entirely, I'm happy with the underseat bass as it is full and punchy.

But the good news end here... There are 2 problems,

- A constant white noise coming from the door speakers and tweeters even when the volume is turned off, I had to adjust the gain all the way to 0 to alleviate this.
- When playing any kind of percussion high pitch sound, it sound harsh, noisy, pronounced and dispersed, I don't how else to describe it, on a lot of the songs it is unbearable when playing at any level of loudness. This can't be normal! Are my tweeters defective?? Do you think this could be the same as the white noise problem?

Needly to say I am very disappointed at the moment, with time and $$$ premium I paid for the speakers... Can someone tell me what's wrong and how to fix this??

One thing worth mention is I stripped the crossover box to bare circuit so it would fit on the door, I hope that is not the cause, other than that I did a pretty standard installation following what the experts have already done on this forum.

- HiFi HU -> Technic's harness -> XD600
- ch1,2 for front, bridged ch3,4 and ch5,6 for the underseats respectively
- 4 gauge wire for power connection nice and secure. Tried both battery ground and left rear seat ground, but result the same.
- when unplug Technic's RCA inputs from the amp, hissing noise gone, but of course that's the only source input I can't do without it...

this might be way off related to your install. I had speakers in my coupe that i was 'trying out' and the amp was not re-adjusted for them (EQ xovers ect) since with the base system my adjustments are done at the amp. the speakers while playing were clear but guitar notes, some vocals, classic metal type was down right painful to listen to at even moderate volume. its was really harsh. i had never heard anything like it.

I didnt really give them a fair chance before going to the rainbows. but was told that even the best speakers can sound too harsh if the EQ / amp arent set up properly. when i had the profis put in, the amp was re-set up again, and the sound went back to smooth goodness that i once loved.

im not familiar with your amp at all, and while it could be related to the hiss you hear, if the amp has built in adjustable EQ and crossovers then that would probably be the starting point for clearing up the harshness.

I already cut the original connector off for both front speakers and tweeters and I was hoping I'd never have to take those doors apart again, arg!

It could be possible one crossover is defective, less probably both.

I was looking to remove the front speakers variable and concentrate in the possibility of the RCA signal as the source of the problem. In other words, if the noise was still there with the OEM speakers then there must be something wrong in the harness RCA contacts -assuming the same problem with two different amps and two different RCA extension cables.

If the noise goes away with the OEM speakers then the problem must be the crossover circuit.

this might be way off related to your install. I had speakers in my coupe that i was 'trying out' and the amp was not re-adjusted for them (EQ xovers ect) since with the base system my adjustments are done at the amp. the speakers while playing were clear but guitar notes, some vocals, classic metal type was down right painful to listen to at even moderate volume. its was really harsh. i had never heard anything like it.

I didnt really give them a fair chance before going to the rainbows. but was told that even the best speakers can sound too harsh if the EQ / amp arent set up properly. when i had the profis put in, the amp was re-set up again, and the sound went back to smooth goodness that i once loved.

im not familiar with your amp at all, and while it could be related to the hiss you hear, if the amp has built in adjustable EQ and crossovers then that would probably be the starting point for clearing up the harshness.

Kevin, XD600 actually doesn't come with any EQ settings, etc. May have to get a MS8 to alleviate the noise and harsh tweeter issue, but not ready to dump more $$$ into it until I find out the cause and fix.

I was looking to remove the front speakers variable and concentrate in the possibility of the RCA signal as the source of the problem. In other words, if the noise was still there with the OEM speakers then there must be something wrong in the harness RCA contacts -assuming the same problem with two different amps and two different RCA extension cables.

If the noise goes away with the OEM speakers then the problem must be the crossover circuit.

Unplug the tweeters at least and see how this affects the noise.

I see where you are going with this. I can't try that right now, but may have sometime to take the door apart next weekend.

Meanwhile, I just replaced the HU with an ipod and Y RCA cable, the hissing noise is gone when not playing or paused. I think the problem is with the connection and feedback from the HU.

I think I've ruled out the following factors:
- Not an amp issue, tried with 2 amps
- Not a RCA cable issue, I tried with 2 sets of RCA cables
- Not a ground issue - tried 4 ground points
- Not a speaker/tweeter issue. 2 reasons, first I can hear hissing noise distinctively from
both when gain is turned up, 2nd the noise is gone with unplug the HU or replace it with another source ipod

What is left
- HU noise. but this is unlikely, because it wasn't there before.
- Harness connection related problem, it is creating some sort of feedback or harsh connection? Not sure how to test this, any idea? Should I try with another harness?
- Lastly do you think a MS8 equalizer would help with this problem?

Other people have put the same system in and made it work.
Did you use the Technic Harness and wire it according to Technics instructions?
The JL Amps claim to accept balanced inputs yet have RCA instead of twisted
pair Input terminators . I assume the shields on those are not a common ground. What about the level switch for Inputs it is in the right position.

I would try a cheap LOC before buying an MS-8 though you shouldn't have to do that.

Other people have put the same system in and made it work.
Did you use the Technic Harness and wire it according to Technics instructions?
The JL Amps claim to accept balanced inputs yet have RCA instead of twisted
pair Input terminators . I assume the shields on those are not a common ground. What about the level switch for Inputs it is in the right position.

I would try a cheap LOC before buying an MS-8 though you shouldn't have to do that.

The guy in the above thread(towards the end had some noise issues having to do with input levels.)

Hey ctuna,

What is the level input you are talking about? I feel I am missing something here.

I didn't get any Technic's instruction, I bought his harness from someone else, so just kind of figured it out myself. There is a piece of device that came with the package I couldn't find any use for, is this the key?? Thanks!

There are NO instructions included with the harness from Technic, if there had been, I would have included them.

Actually, the part you are holding is a 20Amp Inline Fuse Holder/Fuse - used for adding a fuse into a circuit. Now that I think about it, it has nothing to do with the harness, I must have got that mixed in with the harness when all my wiring items were in one box and figured it went with the harness - so you got that for free

There IS an Amp Input Mode selection Switch - in configuration I was planning on using, I would have set it to '4 CH' In this mode, with my hookup plan, the Amp CH5&6 (Subs) would have operated with the sum of CH1 & CH3 and CH2 & CH4 Input Signals respectively

To bridge a Pr of channels on this amp you would use the 'Left +' and 'Right -' speaker connectors only (the 'Left -' & 'Right + remain unused). When bridged, each channel will then deliver optimum power into a 4ohm load.

When a Pr of channels are bridged, they will deliver 200W x1 into a 4ohm load or 150W x1 into an 8ohm load. Operating a Pr of bridged channels into a load lower than 4ohms is not recommended by JL.

Because a bridged Pr of channels requires that both channels receive input, you need to connect both left & right inputs to the source unit. Connection of only one input will result in reduced power output, increased distortion & can cause the amp to overheat - so don't do this!

When a Pr of the amps channels are operating in bridged mode, the output will be in Mono. This mono channel can contain 'Right Channel Only Info', 'Left Channel Only Info', or the sum of the info from both the right & left channels. To achieve one of these options, you would configure the inputs to that Pr of channels in one of these (2) ways:

1.Left Channel Only or Right Channel Only
Use a 'Y' adaptor to split the single channel signal into both left & right RCA inputs. This method would be useful when using a Pr of the amps channels to drive left channel speakers only & the other Pr to drive right channel speakers only

2.Left + Right Channel
When bridged & fed by a stereo input, a Pr of the amp's channels will automatically combine the Left & Right channels into a summed mono (left + right) channel. This option is useful when using a Pr of the amp's channels to drive a subwoofer system or a summed mono center channel.

Over the Labor day weekend, I finally put together my upgrade project - the full Jehnert flatline series + XD600/6 amp. I was expecting an easy installation, but it turned out to be a total disaster, well not entirely, I'm happy with the underseat bass as it is full and punchy.

But the good news end here... There are 2 problems,

- A constant white noise coming from the door speakers and tweeters even when the volume is turned off, I had to adjust the gain all the way to 0 to alleviate this.
- When playing any kind of percussion high pitch sound, it sound harsh, noisy, pronounced and dispersed, I don't how else to describe it, on a lot of the songs it is unbearable when playing at any level of loudness. This can't be normal! Are my tweeters defective?? Do you think this could be the same as the white noise problem?

Needly to say I am very disappointed at the moment, with time and $$$ premium I paid for the speakers... Can someone tell me what's wrong and how to fix this??

One thing worth mention is I stripped the crossover box to bare circuit so it would fit on the door, I hope that is not the cause, other than that I did a pretty standard installation following what the experts have already done on this forum.

- HiFi HU -> Technic's harness -> XD600
- ch1,2 for front, bridged ch3,4 and ch5,6 for the underseats respectively
- 4 gauge wire for power connection nice and secure. Tried both battery ground and left rear seat ground, but result the same.
- when unplug Technic's RCA inputs from the amp, hissing noise gone, but of course that's the only source input I can't do without it...

Thanks for looking!

Someone reading this might get the impression that you bought poor equipment. You seem to have bought nice equipment - in fact, you seem to have bought the branded gear we suggested when you emailed us (but without the parts we include to make everything foolproof, plug-and-play, and easy).

I don't know where you bought it, and given that you wired the crossovers yourself - no offense meant, but I have no idea if you wired the speakers correctly either. That's why we provide that speaker in-door plug-and-play harness which you mentioned in an earlier post - so that there's no possibility of anyone getting any of the connections wrong.

(By the way, I don't know how you mounted the circuit board, but if you used anything with a metallic surface, such as sound damping material with aluminum, or even metallic duct tape...)

Did you use twisted-pair RCA from the Technic harness to the amp input?

I've followed your hiss problem posts, and the last thing you need to do is add more gear. You've seen our customers post that they haven't had hiss problems with this amp unless the gains are too high, and I haven't seen hiss problems with this amp myself. I've also heard these speakers, and I know that when everything is properly connected, this gear should sound great.

I think I've ruled out the following factors:
- Not an amp issue, tried with 2 amps
- Not a RCA cable issue, I tried with 2 sets of RCA cables
- Not a ground issue - tried 4 ground points
- Not a speaker/tweeter issue. 2 reasons, first I can hear hissing noise distinctively from
both when gain is turned up, 2nd the noise is gone with unplug the HU or replace it with another source ipod

What is left
- HU noise. but this is unlikely, because it wasn't there before.
- Harness connection related problem, it is creating some sort of feedback or harsh connection? Not sure how to test this, any idea? Should I try with another harness?
- Lastly do you think a MS8 equalizer would help with this problem?

Replacing the OEM HU balanced outputs with the iPod non-balanced outputs will give you different results by themselves, so it is not a valid comparison.

In the non-balanced signal the ground is part of the signal, and it is also a ground that it is not shared with the car -you have the iPod in your hand. None of that applies to the OEM HU -the output signal does not have any ground and the ground of the OEM HU is shared with other devices in the car.